1. Field of the Invention
The present invention relates to a fan and shroud assembly used for an air blast in an air conditioner of a car, and more particularly, to a fan and shroud assembly which can effectively reduce noise by controlling generation of swirling airflow and backflow during the air blast by rotation of a fan.
2. Background Art
In general, an air conditioner for a car comprises a radiator, and an axial fan for cooling heat exchange medium flowing through a heat exchanger such as a condenser. As shown in FIG. 1, the axial fan 200 generally comprises a hub 230 connected with a shaft of a driving source such as a motor, and a plurality of blades 210 radially arranged on the outer periphery of the hub 230. The axial fan 200 may further include a fan band 220 connecting ends of the blades 210 to prevent transformation of the blades 210. Therefore, air can be axially blown by the blades 210 while the axial fan 200 is rotated by rotational force transmitted from the driving source to the hub 230. A shroud is fixed to the heat exchanger in order to effectively guide the blown air toward the heat exchanger. The shroud has a blast inlet as large as the axial fan can be rotatably inserted thereinto to guide the air blast in such a way as to support the motor.
As shown in FIGS. 2, 3 and 4, the shroud 100 of a puller type fan shroud assembly mounted on the rear of the heat exchanger to inhale air from the front of the heat exchanger and send air to the rear of the heat exchanger comprises: a housing 110 having a blast inlet 120 in which an axial fan 200 is rotatably inserted; a motor supporting ring 130 for supporting a motor (not shown) rotating the axial fan 200 at the center of the blast inlet 120 of the housing 110; and a plurality of guide vanes 140 for radially connecting the motor supporting ring 130 and the housing 110 with each other to support the motor supporting ring 130 and guide air discharged when the axial fan 200 is rotated.
The housing 110 is depressed to the rear to effectively guide sucked air toward the air blowing hole 120, and comprises connection ribs formed on the edges for coupling between the housing 110 and the heat exchanger.
The blast inlet 120 is formed by a guide ring 150 protruding backwardly from the housing 110 and curved from the rear end of the guide ring 150 toward the inside of the guide ring 150, and further comprises a bell mouth 180 for smoothly guiding a discharge of air.
Here, a plurality of swirl preventing saw teeth 160 are formed along the inner periphery of the blast inlet 120, that is, inner periphery of the guide ring 150. In the case where the bell mouth 180 is provided, the swirl preventing saw teeth 160 are formed integrally on the inner periphery of the guide ring 150 which is connected with the bell mouth 180.
The swirl preventing saw teeth 160 are spaced apart at a predetermined interval from the ends of the blades 210 of the axial fan 200. The swirl preventing saw teeth 160 comprise a first side 162 toward the rotational direction of the axial fan and a second side 164 toward the counter-rotational direction of the axial fan.
Such shroud having the swirl preventing saw teeth can reduce noise, but noise generated from the fan and shroud assembly is more increased when noise generated from the car is added. To solve the above problem, a configuration to which a bended bell mouth is provided to smoothly discharge air into the guide ring has been proposed. However, such configuration has a problem in that it is insufficient in reducing noise since it needs additional structure.